implemented various task features:

- saving on CTRL+S
- editing of
    - start date
    - due date
    - members

frontend/src/routes/task/Add.svelte

@@ -75,6 +75,14 @@
         return Object.fromEntries(candidates);
     }
 
+
+    function onkeydown(e){
+        if (e.ctrlKey && e.keyCode === 83) {
+            e.preventDefault();
+            saveTask();
+        }
+    }
+
     async function saveTask(){
         var url = api('task/add');
         const resp = await fetch(url,{
@@ -103,7 +111,7 @@
 
 <fieldset>
     <legend>{t('add_task')}</legend>
-    <table>
+    <table {onkeydown}>
         <tbody>
             <tr>
                 <th>